158 Scientific Intelligence. 



inent fault fissure or closely connected with one. Ores of the third 

 class have also contributed largely to the total output. 



The ores were undoubtedly originally sulphides deposited by 

 ascending solutions. The igneous rocks of the district probably 

 have had an intimate influence on their formation by supplying 

 material together with heat and chemical activity to the under- 

 ground waters. 



The report closes with a detailed description of some of the 

 more important mines, including maps and sections of the work- 

 ings, w. E. E. 



No. 16. — The Carboniferous Formations and Faunas of Colo- 

 rado; by George H. Girty. 546 pp., 10 pis. The first 216 

 pages of this work are devoted to a useful review of the litera- 

 ture and discussion of the interpretations of the geology and 

 paleontology of the Colorado region given by previous writers. 

 In the second part, pp. 217-267, the author discusses the faunal 

 evidence and correlations furnished by the material under inves- 

 tigation; and in the remainder of the volumes (pp. 268-546) the 

 species are described and figured. 



The result of study of the collection shows the presence of 

 both Mississippian and Pennsylvanian faunas. 



The Mississippian fauna occurs in the Leadville limestone and 

 its equivalents, the Ouray and the Millsap limestones. These are 

 interpreted as equivalent to the Kinderhook and lower Burlington 

 faunas of the Mississippi valley region. 



To the Pennsylvanian are referred the Hermosa, Weber, 

 Maroon, Robinson, Molas, and Rico formations. Essentially the 

 same fauna is reported from the Hermosa, Weber, Lower Maroon 

 of the Crested Butte section, and from the Weber shales and 

 grits of the Leadville section. This fauna is considered by the 

 author to be older than any of the Pennsylvanian beds of the 

 Kansas and Nebraska sections. The Rico formation is by its 

 fauna interpreted as probably of about the horizon of the Deer 

 Creek, Hartford and Howard formations of Kansas. h. s. w. 



No. 17. Geology and Water Resources of Nebraska West of 

 the One Hundred and Third Meridian; by N. H. Darton. 66 

 pp., 43 pis., 23 figs. With a few minor changes this paper is a 

 reprint of pp. 719-785 in the Nineteenth Annual Report. 



No. 19. — Contributions to the Geology of Washington. 98 pp., 

 20 pis., 3 figs. This publication contains two papers: Geology 

 and Physiography of Central Washington; by George Otis 

 Smith, and Physiography and Deformation of the Wenatchee- 

 Chelan District, Cascade Range; by Bailey Willis. During 

 Pliocene time a lowland surface was developed in Central Wash- 

 ington and the ancient controlling drainage system may possibly 

 be indicated. This plain was uplifted and warped so that the 

 Cascade range is complex in type. Geologic processes worked 

 rapidly in this region, as is shown by the Eocene section of 10,000 

 feet divisible into four distinct formations, separable both by 

 physical breaks and differences in fossil flora. The unique char- 



